1. Field of the Invention
This invention is in the field of weight lifting equipment. More specifically, this invention relates to a weight lifting system, e.g., a dumbbell or barbell system, with an internal cam mechanism.
2. The Relevant Technology
Hand-held weights such as barbells and dumbbells have been used for many years by exercisers engaging in weightlifting. Some hand-held weight systems include a bar configured to removably receive a variety of different weights which slide onto the bar. Other weight systems include a handle and disks integrally attached on opposing sides of the handle.
It is common for commercial gyms and home gyms to include barbells or dumbbells which are stored on a bench or on the floor. These hand-held weights are used for exercises such as a military press to strengthen the upper body, curls to strengthen the biceps, and squats to strengthen the upper and lower body. Sometimes dumbbells are held while jogging or running in place to enhance the exercise experience.
While lifting a weight which is too small may not provide the adequate training desired by a user, lifting a weight which is too heavy may strain or injure the user. The exerciser may be interested in lifting a lighter weight on one day, then ramp up to a heavier weight on another day. Thus, for the sake of safety and for the appropriate amount of exercise, it is useful to provide a variety of options for the exerciser.
In order to permit a number of different users to lift handweights, it is common for gyms to provide a variety of different weights and sizes of integral or adjustable weights. Despite the advantages of having a variety of different handweights, however, providing an assortment of different handweights is expensive and increases the amount of storage space required. In order to use space more efficiently, gyms typically include a shelf or cabinet for receiving differently-sized handweights.
In the event a weight bench or cabinet is not employed, the user is often forced to leave the weights on the floor, which is a highly inefficient use of space and provides a cluttered appearance. Thus, in order to use space more efficiently, the user is required not only to purchase the assortment of handweights but must also purchase a bench or cabinet for storing the various handweights.
Another problem within the art is that it is often cumbersome to mount weights onto a bar. Weights sometimes include holes therein and are disposed about the bar without being otherwise secured to the bar. One disadvantage with these weights is that it is possible for one or both of the weights on opposing sides of the bar to fall off. This can be inconvenient or even dangerous for the user or for a person adjacent to the user such as a spotter or coach.
For example, if the exerciser is lying on a bench performing a military press and a weight on one side of a bar falls off the bar, the weight on the other side of the bar causes the bar to tip toward the weighted side. If this action occurs suddenly, the non-weighted side can be quickly thrust toward the weighted side, possibly causing injury or damage.
In other embodiments, weights are prevented from falling from a bar through the use of screws disposed through circular brackets coupled outside the weights to the bar. These mechanisms, however, are often inconvenient to mount onto the bar and remove from the bar. Each of these mechanisms must be placed onto the bar separately and on opposing sides of the bar. Another problem within the art is the expense of purchasing separate pieces of equipment for each different weight desired to be used by the weightlifter.
One product known as the POWERBLOCK attempts to provide a selectorized dumbbell which allows a user to select a desired weight to be lifted from a set of stacked weights. A user inserts a core having an internal band grip into a set of stacked weights, then selects a desired number of weights using a selector pin.
The POWERBLOCK however, interferes with the natural movement of the user's wrists and has an unusual rectangular block appearance. The user must reach into the rectangular structure to pick up the weights. As a result, the rectangular structure can inconveniently contact the wrists during use. In addition, the removable selector pin can be lost or misplaced and is inconvenient to orient into and remove from the weights. The pin must also be mounted from a location remote from the location where the practitioner grasps the handle.
It would therefore be an improvement in the art to provide a weightlifting system that is convenient to use and store and enables convenient adjustment of the amount of weight thereon.